将字段改为必填或非必填
alter table TABLENAME MODIFY TABLECOLUMN tinyint(3) null / not null 表中添加字段
ALTER TABLE sys_role ADD role_type varchar(16) not null DEFAULT '' AFTER role_key;查询不同分组的前五个值
select a.* from table_name a (select group_cocat(id order by id desc) as ids from table_name cc group by cc.column) as b where find_in_set(a.id,b.ids) between 1 and 5 order by a.column ,a.column desc
查询数据库表结构
select column_name,column_type,character_maximum_length,if(is_nullable = 'YES','Y','N'),if(column_key = 'PRI','Y','N'),column_default,column_comment from information_schema.columns where table_schema='database_name' and table_name='table_name'
-- table_name 条件可以省略查询数据库表注释
select table_name,table_comment from information_tables where table_schema='database_name' group by table_name查询数据库表字段的注注释
show full columns from table_name;查询整个数据库表字段注释
select b.table_name,b.table_comment,column_name,column_type,column_comment from information_schema.columns a ,information_schema.tables b where a.table_name = b.table_name and a.table_name = "table_name"
